Environmental friendliness is the objective in production and life in the human society nowadays and in the future. Low-carbon and green transport is also the future trend and development direction. Electric bicycles have characteristics such as economy and environmental friendliness, and therefore become desirable exercise devices and vehicles.
An existing electric bicycle is usually assembled with a mid-motor. A mid-motor refers to a motor drive assembly installed at a bottom bracket of an electric bicycle as compared with a front hub motor and a rear hub motor of the electric bicycle. Currently, more and more mid-motors are installed with a torque sensor. The torque sensor detects a pedaling torque during riding, and sends a detected signal to a system controller to synchronously adjust a rotational speed and output power of the motor, so as to keep a direct proportion relationship between the riding torque and the output torque of the motor, thereby achieving an objective of multiplying the torque.
CN103661762A disclosed an electric assist electric bicycle and a mid-motor drive system of the electric assist electric bicycle. The mid-motor drive system of the electric assist electric bicycle includes a first stage end-cover component, a second stage end-cover component, a shell component, a torque sensor component, a motor component, a central shaft component, a planetary reduction mechanism, a clutch mechanism, and a crankset and sprocket component. The planetary reduction mechanism bears all the output torque and is the weakest member in the entire transmission system. With the long-term use of the drive system, the planetary reduction gear has a severe wear problem, which significantly lowers the stability and safety of a mid-drive apparatus.
In addition, an existing torque sensor used for a mid-motor of an electric bicycle is usually a strain gauge sensor. In such a sensor, a strain gauge is disposed on a central shaft of the mid-motor, and a sensor disposed on an outer side of the central shaft then transfers a sensing signal sent by the strain gauge to a controller. Because the strain gauge rotates with the central shaft, the distance between the strain gauge and sensor keeps varying, and therefore a signal is subject to a great extent of attenuation or loss during transmission, resulting in that the controller fails to accurately calculate a pedaling torque of a rider.